Comb filters have use in various applications. One application includes the removal of a fundamental sinusoidal signal and its harmonics from a signal of interest (SOI).
Existing comb filtering techniques have practical limitations. A first technique includes the use of a finite impulse response (FIR) filter. Although this technique is fast and simple, it typically has a poor frequency response. A second technique involves the use of an infinite impulse response (IIR) filter. Theoretically, a sharp notch filter can be created with a lower-order IIR filter than produced with an FIR filter. However, the poles of such a filter must be very close to the unit circle, which causes stability and performance problems when the filter coefficients are quantized for implementation. A third technique involves transforming a block of data samples into the frequency domain using a Fast Fourier Transform (FFT) (or, more generally, a discrete Fourier Transform), and zeroing the bins (“zero-binning”) of the frequencies associated with the interference and its harmonics. An inverse transformation back to the time domain produces the filtered output data. This technique produces acceptable results, but has limited application due of its computational complexity.